The Three-Dimensional Structure of Molecules - Isomerism

Structure Theory in Organic Chemistry

To understand the behaviour of molecules it is important to know their three-dimensional structure. For example, questions could be whether the atoms of a molecule are arranged linearly or angularly? Has the molecule a flat or spatial shape? As a result of their tiny size, molecules are not visible and their structure can only be elucidated in an indirect way. The structure of a molecule is inferred from its behavior. Firstly, it is important to know the composition of a molecule. The information about the type and the atomic ratio of elements, yielded by elementary analysis of a large number of compounds, results in the following general statement:

Dependent of its position in the periodic system, all elements can only have a certain number of bonds. This is called valency.